This invention relates to powder metallurgy and in particular to the dispersion hardening of titanium or titanium alloys with yttria. In addition, the invention is also applicable to other metal or metal alloy matrices such as niobium, iron, nickel, cobalt based alloys, and aluminides of titanium and nickel.
There is considerable need to increase the elevated temperature strength and the use temperature of metal alloys, in particular, titanium structures. One approach to this problem is to reinforce the titanium with ceramic particulate material via powder-metallurgy process. The reinforced structure is fabricated by hot consolidation of the blended powder mix in a vacuum enclosure.
Titanium is extremely reactive with almost all materials at high temperatures with resultant embrittlement and/or formation of brittle intermetallic compounds. Therefore, the problem of increasing the strength of titanium at high temperatures has been extremely difficult to achieve.
U.S. Pat. No. 4,601,874 discloses a process of forming a titanium base alloy with small grain size which includes mixing the titanium alloy with rare earth oxides such as yttria and Dy.sub.2 O.sub.3. The addition of these materials is in very small amounts. Moreover, the usual form of yttria utilized in the '874 patent is a fine powder which is really not suitable for use as a reinforcement material for a metal composite.
U.S. Pat. No. 3,507,630 discloses the dispersion hardening of zirconium using fused yttria. It does not disclose the use of fused yttria and titanium or any other alloy.